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Pitanga HAT

Raspberry Pi HAT with Retro LED Displays and buttons

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Pitanga is a Raspberry Pi HAT incorporates six 5x7 early-style LED displays, driven by the HT16K33 LED driver. The HT16K33 is versatile, easy to use, and affordable — we might even call it the "jelly bean" LED driver, as Dave Jones from EEVblog would say :)

Pitanga HAT is a custom Raspberry Pi HAT featuring six retro 5x7 LED displays driven by the versatile HT16K33 LED driver. It combines vintage aesthetics, acting as both an output display and a basic input device

pca9306.pdf

PCA9306 Datasheet

Adobe Portable Document Format - 1.44 MB - 01/31/2025 at 15:10

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LTP-305G.PDF

LTP-305G Datasheet

Adobe Portable Document Format - 122.31 kB - 01/31/2025 at 15:10

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HT16K33.PDF

HT16K33 Datasheet

Adobe Portable Document Format - 2.19 MB - 01/31/2025 at 15:09

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PitangaHat_v2.1a.zip

Gerber

Zip Archive - 206.61 kB - 01/26/2025 at 16:50

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  • Inspiration and beginnings

    Andrew Tudoroi01/26/2025 at 16:29 0 comments

    Inspiration and Beginnings

    I’ve always been drawn to retro LED displays. While exploring Raspberry Pi extension HATs, I came across Pimoroni’s micro-LED board. I was immediately hooked and decided I needed one. Unfortunately, I wasn’t able to get my hands on it. This setback inspired me to try my hand at PCB design, making this project my very first — from initial design all the way to ordering PCBs from well-known manufacturers.

    For this project, I chose KiCad as my design tool for several reasons:

    • It’s open-source.
    • Highly recommended across the internet and by electronics enthusiasts (I’ve spent countless hours watching related videos 😄).
    • It has a supportive community.

    I wanted my design to be relatively easy to solder, even with a basic soldering iron. Cause that is what i had  at that moment  After researching options, I discovered the HT16K33 LED driver. It turned out to be the a god fit it supports 8x16 mode,  with counting  of the decimal dot on the LTP305 displays  i needed 18x7 which i achieved by rewiring cathodes and some anodes of the displays and later deal with this in software, also HT16k33 is capable of supporting button (keys) for input functionality.

    After some trial and error, I successfully produced Gerber files for my PCB design. Despite some beginner mistakes, the PCBs were manufacturable and functional!

    First trials:

    Next revision:

    With this in mind, I designed the board to include four through-hole buttons and decided to make it a Raspberry Pi HAT. While brainstorming a name, I drew inspiration from fruits — particularly the 8devices Rambutan board sitting on my desk. Thus, the Pitanga Raspberry Pi HAT was born!

    This HAT functions as a simple display for user output and a basic input device — almost like a joystick. I also included pads for an STM 8-pin ARM M0 microcontroller, though I never ended up populating it on the board.

    Challenges and Improvements

    One challenge I encountered was power compatibility. While the Raspberry Pi can sometimes work with I2C devices at 5V logic levels, this isn’t ideal for long-term use. To address this, I connected the HT16K33 to the Raspberry Pi's 3.3V I2C bus. However, the HT16K33 datasheet specifies a voltage range of 4.5V to 5.5V for optimal operation. Despite this mismatch, my setup worked fine during testing.

    To ensure better reliability, I searched for a proper solution and found the PCA9306DP, a dedicated I2c logic level converter chip. It converts the Raspberry Pi’s 3.3V logic levels to 5V for the LED driver.

    With this improvement in mind, I designed a new revision of the board. This version included an additional button, bringing the total to five, and incorporated I2C logic transceivers. After assembling the updated PCBs, the result was a polished Pitanga HAT :)

    Back side:

    Exploring Retro LED Display

    An entirely separate and interesting part of this project was discovering compatible LED displays for the design. While researching, I stumbled upon some displays that are essentially replicas of replicas of replicas of the original models. Despite this, they retain their retro charm and work perfectly with the project. During my search, I also came across this page on Industrial Alchemy, which was an interesting find related to these displays.

    LTP-305R on Raspberry Pi 3A+


    Pintaga HAT with LTP-305R displays modules connected to thinkpad VGA I2C pins

    LTP-305G with Raspberry Pi 4


    ALS340A1

    • Monsanto MAN 2
    • IEE - LRT1704R
    • DIALCO 745-0005
    • Lite-On LTP-305
    • Texas Instruments TIL-305
    • ALS340A
    • ALS340A1
    • 3LS340
    • 3LS363
    • AL104

    Each of these displays carries its own unique story and nostalgic appeal, adding character to the project.

    Final Thoughts

    The Pitanga Raspberry Pi HAT was born from my love of retro tech and the drive to learn. Designing my first PCB and improving it along the way was both challenging and rewarding. If you love retro displays or want to dive into PCB design, I hope...

    Read more »

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cp wrote 5 days ago point

This is awesome!  I also missed out on getting a Pimoroni’s micro-LED board.  Could you share where you were able to purchase the LTP-305R and LTP-305G and any of the other replicas of these?  Thank you!

  Are you sure? yes | no

Andrew Tudoroi wrote 5 days ago point

Thanks! Yeah, these displays are getting harder to find. Right now, there are a few good options on

 eBay https://www.ebay.com/sch/i.html?_nkw=til305&_sacat=0&_from=R40&_trksid=p4432023.m570.l1313

on AliExpress tend to be higher than what’s currently listed on eBay

https://www.aliexpress.com/item/1005005986977945.html?spm=a2g0o.productlist.main.1.2fe1zMlNzMlNf0&algo_pvid=384f997d-7803-485b-bfec-b3f01f5f736c&algo_exp_id=384f997d-7803-485b-bfec-b3f01f5f736c-0&pdp_npi=4%40dis%21EUR%219.99%219.99%21%21%2173.78%2173.78%21%40211b813b17387888425026395e4e14%2112000035191075121%21sea%21NL%213294616139%21X&curPageLogUid=Utv0z0bQ7gqs&utparam-url=scene%3Asearch%7Cquery_from%3A

Another good alternative is the LTR-1704, which should work just fine:
https://www.electronicsurplus.com/iee-industrial-electronic-engineers-lrt1704r-opto-display-5-x-7-dot-matrix

I got my LTP-305R and LTP-305G from AliExpress, and I also managed to find some Soviet ALS340 and ALS340A1 displays on local markets.

Unfortunately, these displays aren’t exactly cheap, but I think they look really cool, and I really wanted some :).

  Are you sure? yes | no

Andrew Tudoroi wrote 5 days ago point

Also you may find interesting this project: https://hackaday.io/project/161694-diytil305

  Are you sure? yes | no

kristina panos wrote 5 days ago point

Hiya Andrew, this looks fantastic! I wrote it up for the blog, and it should publish soon. Keep up the good work! :)

  Are you sure? yes | no

Andrew Tudoroi wrote 5 days ago point

Hi Kristina, thanks so much! I really appreciate it. Looking forward to seeing it on the blog. :)

  Are you sure? yes | no

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